Pest Management Practices for Home and Landscape

Mites

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Several types of mites feed on and damage ornamental plants and trees common in Mississippi. Two groups of these mites are the spider mites and the eriophyid, commonly called gall or rust mites.

Spider Mites

Spider mites found in Mississippi are the European red mite, oak mite, southern red mite, and the twospotted spider mite. European and oak mites occur only sporadically, but high infestations may severely damage fruit and oak trees. The southern red mite and twospotted spider mite occur more frequently and feed on a wide range of plants.

Southern red mites are often found on broadleaf evergreens such as American holly, azalea, sasanqua, camellia, or Japanese holly. Other host plants include rhododendron, boxwood, and laurel. Twospotted spider mite infestations may occur on roses, marigolds, chrysanthemums, needled evergreens, pyrancantha, and clematis.

These two mites develop similarly in the number of stages from egg to adult; however, the time spent in each stage varies. The following is an example of the development of twospotted spider mite at 85 ¼F.

The female twospotted spider mite begins laying eggs about 2 days after molting from the second nymphal stage. The turn-around time from egg to egg is about 6 to 8 days. Dry, hot weather (85-95 ¼F) is most favorable for twospotted spider mite reproduction. Under these conditions, a female deposits two to six eggs per day, with an average of 100 over her life span.

The southern red mite is more likely to occur in milder temperatures (70-80 ¼F), which lengthens the life cycle. It usually takes about 2 weeks from egg to egg. The twospotted spider mite overwinters as an adult in protected areas on the plant, whereas the southern red mite overwinters in the egg stage.

Damage -- Mite colonies usually begin on the undersides of the leaves. As the populations grow, mites may spread to both leaf surfaces, and in the case of the twospotted spider mite, noticeable amounts of webbing are present. All mite stages can be found within and beneath this webbing.

Both nymphs and adults feed by piercing the leaf surface with needle-like mouthparts and sucking up plant sap. Damage first appears as a flecking or stippling of the foliage. As feeding continues, leaves become lighter in color because green chlorophyl is being removed. Heavily damaged leaves turn tan or bronze; this bronze color is particularly symptomatic of southern red mite damage on camellias. Leaves finally dry out and fall from the plant.

Eriophyid Mites

Mites within this group are very small (0.5 mm long) and are rarely seen even with the aid of a 10X hand lens. They are generally colorless and are often identified by the damage they cause. The mites attack a wide range of plants, including maples, camellias, hackberry, American elm, willow, and ash. They are one of the few mites or insects that feed on poison ivy or poison oak. Unfortunately, the damage is not enough to kill these plants. The life cycles of the eriophyid mite are not very well understood.

Damage -- Damage is caused by the mites’ feeding on individual plant cells. The resulting abnormalities may be bud gall, blister, a rust-like growth on the leaves, or browning of leaves and bud scales. The following is a description of the abnormalities that occur on particular plants. The scientific name of the mites is given because they do not have common names.

Red Maple. The mite Vasates quadripedes causes a leaf gall. The gall is a small (1 to 2 mm) beadlike growth on the top of the leaf. The inside is hollow. In heavy infestations the leaves curl, form cylindrical rolls,and drop prematurely. In summer the mite can be found in the galls. As the galls become discolored, the mites migrate to trunk and branches. They overwinter under bark scales.

Sugar Maple. The mite Eriophyes elongatus causes a red rust-like growth on the top of the leaf. It, or a related species, causes a similar growth on silver maple. At the beginning, the rust-like patches are greenish-white before turning red. The density on the leaf varies, depending on the number of mites present. Occasionally, the growth causes leaf distortion and premature leaf drop. To cause this condition, as much as 10-20 percent of the leaf is covered.

Camellia. The mites Acaphylla steinwedeni, Calacarus carinatus, and Cosetacus camellia attack camellia leaves and buds. The Cosetacus camellia causes the bud scales and floral parts to brown, beginning at the edges and moving inward. This eventually causes premature bud drop. The mite also causes a rusty condition on the leaves. The first two mites cause the leaves to turn brown and fold down. Damage is similar to cold damage.

Suggestions To Control Spider Mites and Eriophyid Mites on Ornamental Plants

1. Early Detection -- Routinely check shrubs and annuals for mites. This will keep damage to a minimum, especially on evergreen plants. Also, fewer mites are easier to control. On several plants, inspect both upper and lower surfaces of several leaves for webbing and/or adult mites. A hand lens or magnifying glass is helpful. Look carefully at leaves that show any unusual color patterns. This is particularly important if the plant is not suffering from other stresses such as lack of water or plant nutrients.
   
2. Non-Chemical Control -- If only a few plants are infested and you can reach the plants with a garden hose, it might be possible to wash the spider mites from the plants. Use enough pressure to wet thoroughly both leaf surfaces. The water force may dislodge the mites or kill them. Water will not affect the egg; therefore, repeat the procedures in 3 to 5 days. If the initial mite infestation is large, a third washing is helpful.
   
3. Chemical Control -- If chemical control is needed, spray coverage and repeat applications are important. Many of the miticides used must come in contact with the pest to achieve control. This means directing your spray to the undersides of the leaves where most of the mites are.

Coverage may be better if you add a spreader to the spray mixture. This material helps spread the solution over the leaf surface. This would be especially helpful on thick, waxy leaves such as camellia and holly. But remember, direct your spray where the pest is located.

Repeat Applications: The miticides control adults and immatures but do not affect the eggs. It takes 2 to 3 days for eggs to hatch. This means you must make a second application to kill newly-hatched nymphs. A third application may also be needed.

By Dr. James H. Jarratt, Extension Entomologist

Information Sheet 1297
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of Congress, May 8 and June 30, 1914. JOE H. MCGILBERRY, Interim Director

(rev 500-8-01)

Copyright 2001 by Mississippi State University. All rights reserved.

This document may be copied and distributed for nonprofit educational purposes provided that credit is given to the Mississippi State University Extension Service.

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